### Correct Option: A. 30 degrees ### Detailed Explanation: When light strikes a surface, such as a flat mirror, it follows a fundamental principle known as the law of reflection. This law states that the angle of incidence is equal to the angle of reflection. 1. **Understanding the Terms**: - **Angle of Incidence (i)**: This is the angle formed between the incoming ray of light and the normal (an imaginary line perpendicular to the surface at the point of incidence). - **Angle of Reflection (r)**: This is the angle formed between the reflected ray of light and the normal. 2. **Applying the Law of Reflection**: - According to the law of reflection: \[ \text{Angle of Incidence} (i) = \text{Angle of Reflection} (r) \] - In this case, the angle of incidence is given as 30 degrees. Therefore, we can directly apply the law: \[ r = i = 30 \text{ degrees} \] 3. **Conclusion**: - Since the angle of incidence is 30 degrees, the angle of reflection is also 30 degrees. Thus, the correct answer is **A. 30 degrees**. ### Why Other Options Are Incorrect: - **Option B: 60 degrees**: - This option suggests that the angle of reflection is greater than the angle of incidence. According to the law of reflection, this is not possible. The angle of reflection must equal the angle of incidence, so this option is incorrect. - **Option C: 90 degrees**: - This option implies that the light reflects at a right angle to the normal. For this to be true, the angle of incidence would have to be 90 degrees, which is not the case here. Therefore, this option is also incorrect. - **Option D: 15 degrees**: - This option suggests a much smaller angle of reflection than the angle of incidence. Again, according to the law of reflection, this cannot happen. The angle of reflection must match the angle of incidence, making this option incorrect as well. ### Common Pitfalls: - **Confusing Angle of Incidence with Angle of Reflection**: Remember that these two angles are always equal in the case of reflection. - **Misunderstanding the Normal Line**: The normal line is crucial for measuring angles. It is always perpendicular to the surface at the point of incidence. - **Forgetting the Law of Reflection**: Always recall that the law of reflection is a fundamental principle that applies to all reflective surfaces. ### Revision Summary: - The angle of incidence equals the angle of reflection (Law of Reflection). - For a beam of light striking a mirror at 30 degrees to the normal, the angle of reflection is also 30 degrees. - Incorrect options arise from misunderstanding the relationship between incidence and reflection angles. - Always visualize the normal line to accurately measure angles in reflection problems.